Since becoming chief justice of the United States in 2005, John Roberts has been on a mission to lift the US Supreme Court above the partisan politics that has consumed other American institutions, trying to insulate the court from the public’s overall declining confidence in the federal government.

His success to date has been mixed, to put it mildly. The election of Donald Trump last week – which Republicans see as vindicating GOP senators’ ongoing refusal to fill a vacancy on the high court – will only test that mission further.

Some would argue that there is little nonpartisan legitimacy left for the court to maintain. For the past year more Americans have disapproved of the court than approved, according to Gallup – 15 years ago, approval hovered between 50 and 60 percent. Pew reported that negative views of the court are at a 30-year high, driven in part by a widespread perception that the justices are unable to set aside their political views when making decisions.

That perception may only be further entrenched after the Supreme Court became a central issue of the presidential campaign – due to Republican senators’ refusal to appoint President Obama’s nominee to the court, Merrick Garland, on the grounds that the next president should make that choice.

Since Justice Antonin Scalia passed away in February, the battle to fill his seat has “given the impression that politicians are willing to make the court political,” says Steven Schwinn, a professor at the John Marshall Law School in Chicago. “And that in turn has given a greater impression that the court itself is political.”

A series of narrowly divided and (since Justice Scalia’s death) evenly split decisions on divisive issues such as immigration, abortion, and affirmative action have further bolstered this impression, Professor Schwinn adds.

“The more rulings the court issues that are closely divided on hot-button issues the more it’s viewed as a political institution,” he says.

Chief Justice Roberts has had some success – putting an emphasis on cases in which the justices agree. But it is a situation that he alone cannot undo, legal experts say. The court is political because politicians have specifically appointed justices – and reshaped the process – to make it so.

That use of the court for partisan purposes is set to intensify, making Roberts’s balancing act even more difficult – and perhaps needed.

“There’s no question that citizens are looking closely at the court,” says Jeffrey Rosen, a professor at the George Washington University School of Law. “That will make it all the more delicate and important for the court to tread carefully if it wants to maintain nonpartisan legitimacy.”

Roberts's hero

Shortly after he joined the high court, Roberts spoke of his desires to emulate John Marshall, chief justice from 1801 to 1835 and a personal hero, and promote unanimity, according to an interview with Professor Rosen in The Atlantic.

“I think he would concede he’s had mixed success so far,” says Rosen.

His success is in the fact that the majority of the court’s decisions are unanimous. In the 2013-14 term, nearly two-thirds were unanimous, the highest proportion since 1940. He’s sought to avoid 5-to-4 and 4-to-4 decisions by focusing rulings on technical legal questions the justices can agree on and leaving it to Congress to set broader legal precedents.

But those strategies have been known to backfire. His votes to uphold the individual mandate of the Affordable Care Act and to gut key provisions of the Voting Rights Act – both justified with the belief that decisions of such magnitude should be made by Congress, not the court – infuriated Republicans and Democrats, respectively.

But the larger challenge Roberts has faced is that his fellow justices have not always been as committed to his cause as he is.

In recent decades, justices have increasingly voted along the same ideological lines as the president who appointed them. That wasn't always the case: Dwight Eisenhower, a Republican, appointed Earl Warren and William Brennan, two of the most liberal justices in the court’s history. John Kennedy appointed Byron White, who opposed the Roe v. Wade decision, which legalized abortion, and Miranda v. Arizona, which ruled that detained criminal suspects must be informed about the right to silence and an attorney before police questioning.

“Now, all the ‘liberal’ justices have been appointed by Democrats, all the ‘conservative’ Justices by Republican Presidents,” wrote Richard Pildes, a professor at the New York University School of Law, in an email to the Monitor.

And the American public has noticed, with 7 in 10 Americans – spanning partisan and demographic groups – believing that the Supreme Court justices “are often influenced by their own political views,” according to the Pew report.

Whose army?

That is damaging, experts say. Since the court relies on the states and other federal branches of government to enforce its rulings, the more politicized it becomes, the less effective it becomes.

“It doesn’t have an army, so at the end of the day [the court] relies on the goodwill of other political actors to enforce its decisions,” says Schwinn.

That may be difficult in the short-term because of how politicized the next appointment to the court will be, says Stephen Vladeck, a professor at the University of Texas School of Law in Austin. “The politicization of the court has really come to a head in the last eight months in the fight over the Scalia vacancy.”

If Roberts and his colleagues are going to restore the court’s reputation as a trusted, nonpartisan counterweight in the federal government, the justices will have to take matters in their own hands.

Given the fallout over the Scalia vacancy, “I think it’s inevitable that there will be an increased perception that the court is a political institution,” adds Professor Vladeck. “The only way for the court to really push back against that perception is to take steps and hand down decisions that are not viewed as being political.”